Hawaii astronomers track down source of short gamma-ray bursts

Hawaii astronomers using the Frederick C. Gillett Gemini Telescope on Mauna Kea have found the source of short flashes of gamma rays from outer space: a collision of two dead stars.

For 35 years, astronomers have been fascinated by mysterious flashes of invisible energy from apparently random places in the sky. These events, known as gamma-ray bursts, last less than a few seconds and were first discovered by U.S. military satellites designed to monitor Russian nuclear tests.

The shortness of the bursts make them difficult to catch, so astronomers had been uncertain whether the bursts were coming from the solar system, the Milky Way or distant galaxies. Research on the short bursts floundered for decades.

But on July 9, 2005, Paul Price of the University of Hawaii Institute for Astronomy and Kathy Roth of the Gemini Observatory received news of a burst detected by a NASA's High Energy Transient Explorer satellite. Tipped off by an X-ray glow from the fading remnant of the explosion, they measured the event to be 1.3 billion light-years away.

Price was ecstatic. "We've finally tracked down a short burst to a small galaxy a long way from our own."

In papers published today in the science journal "Nature," Price and Roth, together with their collaborators at Penn State, Caltech and several other observatories, conclude that the July 9 event must have involved a "neutron star," a rare type of dead star so dense that each cubic inch weighs over a trillion tons. They believe that the outburst occurred when one neutron star collided with either another neutron star or with a black hole.

The two objects had probably been orbiting each other in ever decreasing circles for many millions of years before they finally touched. At that moment, the neutron star was ripped apart by the intense gravity, and everything funneled down a black hole within seconds, which powered the cosmic flash.

"The burst is so energetic that I think it just has to involve a black hole," Roth explained.

If a gamma-ray burst were to occur near the solar system, it would have a major adverse effect on life on Earth. Astronomers already know of at least one similar pair of neutron stars in our own Milky Way galaxy, but these stars are not due to collide for 300 million years.

ABOUT THE INSTITUTE FOR ASTRONOMY

The Institute for Astronomy at the University of Hawaii conducts research into galaxies, cosmology, stars, planets, and the sun. Its faculty and staff are also involved in astronomy education, deep space missions, and in the development and management of the observatories on Haleakala and Mauna Kea.

Established in 1907 and fully accredited by the Western Association of Schools and Colleges, the University of Hawaii is the state‘s sole public system of higher education. The UH System provides an array of undergraduate, graduate, and professional degrees and community programs on 10 campuses and through educational, training, and research centers across the state. UH enrolls more than 50,000 students from Hawaii, the U.S. mainland, and around the world.

ABOUT THE GEMINI OBSERVATORY

The Gemini Observatory is an international collaboration that has built two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located at Mauna Kea, Hawaii (Gemini North) and the other telescope at Cerro Pachón in central Chile (Gemini South), and hence provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in each partner country with state-of-the-art astronomical facilities that allocate observing time in proportion to each country‘s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the UK Particle Physics and Astronomy Research Council (PPARC), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The Observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.